The following identified United States patent applications are relied upon and are fully incorporated herein by reference:
U.S. patent application entitled xe2x80x9cRotating element sheet material with microstructured substrate and method of use,xe2x80x9d by John Christopher Knights, filed on May 3, 2000, and accorded Ser. No. 09/563,504.
U.S. patent application entitled xe2x80x9cRotating element sheet material with generalized containment structure,xe2x80x9d by Nicholas K. Sheridon, filed on Apr. 14, 2000, and accorded Ser. No. 09/549,518.
U.S. patent application entitled xe2x80x9cRotating element sheet material with reversible highlighting,xe2x80x9d by Alexander E. Silverman, filed on Mar. 2, 2000, and accorded Ser. No. 09/517,522.
The present invention relates to a system and method of assembling rotatable elements and to a system and method of assembling laminate substrates for use in rotating element sheet material.
Rotating element sheet material has been disclosed in U.S. Pat. Nos. 4,126,854 and 4,143,103, both herein incorporated by reference, and generally comprises a substrate, an enabling fluid, and a class of rotatable elements. As discussed more below, rotating element sheet material has found a use as xe2x80x9creusable electric paper.xe2x80x9d FIG. 1 depicts an enlarged section of rotating element sheet material 18, including rotatable element 10, enabling fluid 12, cavity 14, and substrate 16. Observer 28 is also shown. Although FIG. 1 depicts a spherically shaped rotatable element and cavity, many other shapes will work and are consistent with the present invention. As disclosed in U.S. Pat. No. 5,389,945, herein incorporated by reference, the thickness of substrate 16 may be of the order of hundreds of microns, and the dimensions of rotatable element 10 and cavity 14 may be of the order of 10 to 100 microns.
In FIG. 1, substrate 16 is an elastomer material, such as silicone rubber, that accommodates both enabling fluid 12 and the class of rotatable elements within a cavity or cavities disposed throughout substrate 16. The cavity or cavities contain both enabling fluid 12 and the class of rotatable elements such that rotatable element 10 is in contact with enabling fluid 12 and at least one translational degree of freedom of rotatable element 10 is restricted. The contact between enabling fluid 12 and rotatable element 10 breaks a symmetry of rotatable element 10 and allows rotatable element 10 to be addressed. The state of broken symmetry of rotatable element 10, or addressing polarity, can be the establishment of an electric dipole about an axis of rotation. For example, it is well known that small particles in a dielectric liquid acquire an electrical charge that is related to the Zeta potential of the surface coating. Thus, an electric dipole can be established on a rotatable element in a dielectric liquid by the suitable choice of coatings applied to opposing surfaces of the rotatable element.
The use of rotating element sheet material 18 as xe2x80x9creusable electric paperxe2x80x9d is due to the fact that the rotatable elements are typically given a second broken symmetry, a multivalued aspect, correlated with the addressing polarity discussed above. That is, the above mentioned coatings may be chosen so as to respond to incident electromagnetic energy in distinguishable ways. Thus, the aspect of rotatable element 10 to observer 28 favorably situated can be controlled by an applied vector field.
For example, as disclosed in U.S. Pat. No. 4,126,854, hereinabove incorporated by reference, rotatable element 10 may comprise a black polyethylene generally spherical body with titanium oxide sputtered on one hemisphere, where the titanium oxide provides a light-colored aspect in one orientation. Such a rotatable element in a transparent dielectric liquid will exhibit the desired addressing polarity as well as the desired aspect.
II.A. Rotatable Elements with Two-valued Aspects
A multivalued aspect in its simplest form is a two-valued aspect. When the aspect is the chromatic response to visible light, rotatable element 10 with a two-valued aspect can be referred to as a bichromal rotatable element. Such a rotatable element is generally fabricated by the union of two layers of material as described in U.S. Pat. No. 5,262,098, herein incorporated by reference. FIG. 2 depicts a method of fabricating a rotatable element with a two-valued aspect described in U.S. Pat. No. 5,262,098. Disk 134 rotates about axis 132. First layer material 21 is applied to rotating disk 134 from the bottom while second layer material 23 is applied from the top. The two materials meet at the edge of rotating disk 134 and form ligament 136. When the centrifugal force imparted to the material overcomes the surface tension responsible for the centripetal force, the two materials form rotatable element 10, depicted in FIGS. 2 and 4. One skilled in the art will appreciate that yield rates for rotatable elements of the proper size, and with the proper proportion of first layer material 21 and second layer material 23 are dependent on a variety of factors. FIG. 3 depicts ligament 136 in enlarged form and FIG. 4 depicts the resulting rotatable element 10. By way of example only, rotatable element 10 is depicted as a generally spherical body. As shown in FIGS. 2 and 4, first layer material 21 and second layer material 23 form first layer 20 and second layer 22 respectively of rotatable element 10.
FIGS. 5-8 depict rotatable element 10 and exemplary systems that use such rotatable elements. In FIG. 5, rotatable element 10 is composed of first layer 20 and second layer 22 and is, by way of example again, a generally spherical body. The surface of first layer 20 has first coating 91 at a first Zeta potential, and the surface of second layer 22 has second coating 93 at a second Zeta potential. First coating 91 and second coating 93 are chosen such that, when in contact with a dielectric fluid (not shown), first coating 91 has a net positive electric charge with respect to second coating 93. This is depicted in FIG. 5 by the xe2x80x9c+xe2x80x9d and xe2x80x9cxe2x88x92xe2x80x9d symbols respectively. Furthermore, the combination of first coating 91 and the surface of first layer 20 is non-white-colored, indicated in FIG. 5 by hatching, and the combination of second coating 93 and the surface of second layer 22 is white-colored. One skilled in the art will appreciate that the material associated with first layer 20 and first coating 91 may be the same. Likewise, the material associated with second layer 22 and second coating 93 may be the same.
FIG. 6 depicts no-field set 30. No-field set 30 is a subset of randomly oriented rotatable elements in the vicinity of vector field 24 when vector field 24 has zero magnitude. Vector field 24 is an electric field. No-field set 30, thus, contains rotatable elements with arbitrary orientations with respect to each other. Therefore, observer 28 in the case of no-field set 30 registers views of the combination of second coating 93 and the surface of second layer 22, and first coating 91 and the surface of first layer 20 in an unordered sequence. Infralayer 26 forms the backdrop of the aspect. Infralayer 26 can consist of any type of material or aspect source, including but not limited to other rotatable elements, or some material that presents a given aspect to observer 28.
FIG. 7 depicts first aspect set 32. First aspect set 32 is subset of rotatable elements in the vicinity of vector field 24 when the magnitude of vector field 24 is nonzero and has the orientation indicated by arrow 25. In first aspect set 32, all of the rotatable elements orient themselves with respect to arrow 25 due to the electrostatic dipole present on each rotatable element 10. In contrast to no-field set 30, observer 28 in the case of first aspect set 32 registers a view of a set of rotatable elements ordered with the non-white-colored side up. Again, infralayer 26 forms the backdrop of the aspect. An alternate view of first aspect set 32 of FIG. 7 is depicted in FIG. 8. In FIG. 8, the symbol ⊙ indicates an arrow directed out of the plane of the figure. In FIGS. 7 and 8, rotatable element 10, under the influence of applied vector field 24, orients itself with respect to vector field 24 due to the electric charges present as a result of first coating 91 and second coating 93.
One skilled in the art will appreciate that first aspect set 32 will maintain its aspect after applied vector field 24 is removed, in part due to the energy associated with the attraction between rotatable element 10 and the substrate structure, as, for example, cavity walls (not shown). This energy contributes, in part, to the switching characteristics and the memory capability of rotating element sheet material 18, as disclosed in U.S. Pat. No. 4,126,854, hereinabove incorporated by reference.
II.B. Rotatable Elements with Multivalued Aspect
A rotatable element with multivalued aspect is generally fabricated in the same manner as rotatable elements with two-valued aspect. FIG. 9 depicts a method of fabricating a rotatable element with six layers as disclosed in U.S. Pat. No. 5,919,409, herein incorporated by reference. Disk 140, disk 142, and disk 144 all rotate about axis 145. As depicted in FIG. 10, indicating a detailed view of ligament 136, first layer material 21 is applied to rotating disk 140 from the top while second layer material 23 is applied to disk 140 from the bottom. Likewise, third layer material 149 is applied to rotating disk 142 from the top while fourth layer material 151 is applied to disk 142 from the bottom. Finally fifth layer material 153 is applied to rotating disk 144 from the top while sixth layer material 155 is applied to disk 144 from the bottom. The six materials meet at the edge of the rotating disks as depicted in FIGS. 9 and 10, and form ligament 136. When the centrifugal force imparted to the material overcomes the surface tension responsible for the centripetal force, the six materials form rotatable element 10, depicted in FIGS. 9 and 11. Again, one skilled in the art will appreciate that yield rates for rotatable elements of the proper size, and with the proper proportion of all six layers of material are dependent on a variety of factors.
An exemplary rotatable element 10 of FIG. 9 is depicted in FIG. 11. As shown in FIGS. 9-11, first layer material 21 forms first layer 20, second layer material 23 forms second layer 22, third layer material 149 forms third layer 148, fourth layer material 151 forms fourth layer 150, fifth layer material 153 forms fifth layer 152, and sixth layer material 155 forms sixth layer 154, of rotatable element 10.
One skilled in the art will appreciate that the choice of the six materials presented here can be manipulated so as to create a rotatable element with two-valued aspect, three-valued aspect, and so-on. For example, if first layer material 21, second layer material 23, and third layer material 149 are all chosen so as to be a first aspect material, and fourth layer material 151, fifth layer material 153, and sixth layer material 155 are all chosen so as to be a second aspect material, then rotatable element 10 of FIG. 11 will have all the usual properties of a rotatable element with a two-valued aspect as presented in FIGS. 2-8. Thus, other choices and combinations of the six materials are apparent to one skilled in the art.
Rotatable elements with multivalued aspect are generally utilized in rotating element sheet material that use canted vector fields for addressing. A canted vector field is a field whose orientation vector in the vicinity of a subset of rotatable elements can be set so as to point in any direction in three-dimensional space. U.S. Pat. No. 5,717,515, herein incorporated by reference, discloses the use of canted vector fields in order to address rotatable elements. The use of canted vector fields with rotating element sheet material 18 allows complete freedom in addressing the orientation of a subset of rotatable elements, where the rotatable elements have the addressing polarity discussed above. Exemplary systems utilizing rotatable elements with three-valued aspects and canted vector fields for addressing are depicted in FIGS. 12-21.
In FIGS. 12-16, second layer 22 separates first layer 20 and third layer 38 in rotatable element 10. As depicted in FIG. 12, the surface of third layer 38 has third coating 95 at a first Zeta potential, and the surface of first layer 20 has first coating 91 at a second Zeta potential such that third coating 95 has a net positive charge, xe2x80x9c+,xe2x80x9d with respect to first coating 91 when rotatable element 10 is in contact with a dielectric fluid (not shown). As above, one skilled in the art will appreciate that the material associated with first layer 20 and first coating 91 may be the same. Likewise, the material associated with third layer 38 and third coating 95 may be the same. The combination of first coating 91 and the surface of first layer 20 is white-colored, and the combination of third coating 95 and the surface of third layer 38 is a first non-white-color, indicated in FIG. 12 by hatching. The surface of second layer 22 is a second non-white color, indicated in FIG. 12 by perpendicular hatching.
In FIG. 13, no-field set 50 depicts a subset of randomly oriented rotatable elements in the vicinity of vector field 24 when vector field 24 has zero magnitude. In no-field set 50, the rotatable elements have arbitrary orientations. Therefore, observer 28 in the case of no-field set 50 registers views of the combination of the surface of first layer 20 and first coating 91, the surface of second layer 22, and the combination of the surface of third layer 38 and third coating 95 in an unordered sequence. Again, infralayer 26 forms the backdrop of the aspect.
FIG. 14 depicts first aspect set 52 of the system introduced in FIGS. 12 and 13. In first aspect set 52, observer 28 registers a coherent view of the combination of the surface of third layer 38 and third coating 95. In first aspect set 52, all of the rotatable elements orient themselves such that the combination of the surface of third layer 38 and third coating 95 lie in the direction indicated by arrow 25, where arrow 25 indicates the direction of vector field 24.
FIG. 15 depicts second aspect set 54 of the system introduced in FIGS. 12 and 13. In second aspect set 54, observer 28 registers a coherent view of the combination of the surface of first layer 20 and first coating 91. In second aspect set 54, all of the rotatable elements orient themselves such that the combination of the surface of third layer 38 and third coating 95 lie in the direction indicated by arrow 25, where arrow 25 indicates the direction of vector field 24.
Finally, FIG. 16 depicts third aspect set 56 of the system introduced in FIGS. 12 and 13. In third aspect set 56, observer 28 registers a coherent view of the surface of second layer 22 as well as portions of the combination of the surface of first layer 20 and first coating 91, and the combination of the surface of third layer 38 and third coating 95. Again, in third aspect set 56, all of the rotatable elements orient themselves such that the surface of third layer 38 lies in the direction indicated by arrow 25, where arrow 25 indicates the direction of vector field 24. The use of a canted vector field, thus, allows for the utilization of more than two aspects of a rotatable element.
Again, one skilled in the art will appreciate that first aspect set 52, second aspect set 54, and third aspect set 56 will maintain their aspect after applied vector field 24 is removed due to the energy associated with the attraction between rotatable element 10 and the substrate structure, as, for example, cavity walls (not shown). This energy contributes, in part, to the switching characteristics and the memory capability of rotating element sheet material 18, as disclosed in U.S. Pat. No. 4,126,854, hereinabove incorporated by reference.
In FIGS. 17-21, rotatable element 10 with a multivalued aspect is a xe2x80x9clight valve,xe2x80x9d as disclosed, for example, in U.S. Pat. No. 5,767,826, herein incorporated by reference. Rotatable element 10 in FIG. 17 is composed of first layer 20, second layer 22 and third layer 38. First layer 20 and third layer 38 are transparent to visible light and second layer 20 is opaque to visible light. The surface of third layer 38 has third coating 95 at a first Zeta potential, and the surface of first layer 20 has first coating 91 at a second Zeta potential such that third coating 95 has a net positive charge, xe2x80x9c+,xe2x80x9d with respect to first coating 91 when rotatable element 10 is in contact with a dielectric fluid (not shown). First coating 91 and third coating 95 are also chosen to be transparent to visible light. As above, one skilled in the art will appreciate that the material associated with first layer 20 and first coating 91 may be the same. Likewise, the material associated with third layer 38 and third coating 95 may be the same.
FIG. 18 depicts no-field set 70. No-field set 70 is a subset of randomly oriented rotatable elements in the vicinity of vector field 24 with zero magnitude. In no-field set 70, the rotatable elements have arbitrary orientations. Therefore, observer 28 in the case of no-field set 70 registers views of the disk corresponding to second layer 22 in unordered orientations and infralayer 26, where infralayer 26 forms the backdrop of the aspect. Again, infralayer 26 can consist of any type of material or aspect source, including but not limited to other rotatable elements, or some material that presents a given aspect to observer 28.
FIG. 19 depicts first aspect set 72 of the system introduced in FIGS. 17 and 18. In first aspect set 72, observer 28 registers a coherent view of the face of the disk of opaque second layer 22.
FIG. 20 depicts second aspect set 74 of the system introduced in FIGS. 17 and 18. In second aspect set 74, observer 28 again registers a coherent view of the face of the disk of opaque second layer 22. Both first aspect set 72 of FIG. 19 and second aspect set 74 of FIG. 20 maximally obstruct infralayer 26, where infralayer 26 can be any type of material or aspect source, including but not limited to other rotatable elements, or some material that presents a given aspect to observer 28. Such a case corresponds to the case of a xe2x80x9cclosedxe2x80x9d light valve.
Finally, FIG. 21 depicts third aspect set 76 of the system introduced in FIGS. 17 and 18. In third aspect set 76, observer 28 registers a coherent view of the disk of opaque second layer 22 edge-on. In this case, infralayer 26 is minimally obstructed by the set of rotatable elements. Such a case corresponds to the case of a light valve that is xe2x80x9copen.xe2x80x9d
One skilled in the art will appreciate that first aspect set 72, second aspect set 74, and third aspect set 76 will maintain their aspect after applied vector field 24 is removed due to the energy associated with the attraction between rotatable element 10 and the substrate structure, as, for example, cavity walls (not shown). Again, this energy contributes, in part, to the switching characteristics and the memory capability of rotating element sheet material 18, as disclosed in U.S. Pat. No. 4,126,854, hereinabove incorporated by reference.
In addition, one skilled in the art will appreciate that no-field set, first aspect set, second aspect set, and third aspect set discussed above in FIGS. 6-8, 13-16, and 18-21 can form the elements of a pixel, where vector field 24 can be manipulated on a pixel by pixel basis using an addressing scheme as discussed, for example, in U.S. Pat. No. 5,717,515, hereinabove incorporated by reference.
Still further, one of skill in the art will appreciate that although opaque second layer 22 is depicted in FIGS. 17-21 as presenting the same aspect in first aspect set 72 and second aspect set 74, second layer 22 may itself have a two-valued aspect such that the orientation associated with first aspect set 72 in FIG. 19 presents a black-colored aspect, while the orientation associated with second aspect set 74 in FIG. 20 presents a light-colored aspect. Such an effect, for example, is achieved when second layer 22 comprises a black-colored disk and a light-colored disk that are stacked as along a common cylindrical axis.
In light of the foregoing, it remains desirable to fabricate and assemble rotatable elements with multivalued aspects for use in rotating element sheet material using a technique with a yield rate that does not depend on the complex processes depicted in FIGS. 2-4 and 9-11, and discussed in U.S. Pat. Nos. 5,262,098 and 5,919,409 respectively, both hereinabove incorporated by reference.
II.C. Laminate Substrate System and Method
A desired property of rotating element sheet material as reusable electric paper is a high overall ratio of effective aspect area to surface area. With respect to chromatic properties, this is related to reflectance and transmittance. Reflectance of currently available reusable electric paper is around 15 to 20%. Reflectance of ordinary paper, however, is of the order of 85%. U.S. Pat. No. 5,808,783, herein incorporated by reference, discloses a method of improving the ratio of effective aspect area to surface area for rotating element sheet material 18 through the use of a dense monolayer of rotatable elements. The arrangement of a dense monolayer of rotatable elements can be made dependent upon the geometry of the cavities contained within substrate 16. U.S. Pat. No. 5,815,306, herein incorporated by reference, discloses an xe2x80x9ceggcratexe2x80x9d substrate suitable for transmissive-type aspects. Thus, it remains desirable to fabricate substrate 16 such that it can accommodate a dense monolayer of rotatable elements. Furthermore, it remains desirable to precisely position composite rotatable-element components to form the dense monolayer within substrate 16.
Accordingly, in one embodiment of the present invention, composite rotatable-element components are assembled from rotatable-element components through the use of two carriers with microstructured surfaces so as to accommodate rotatable-element components of a first class on a first carrier microstructured surface, and rotatable-element components of a second class on a second carrier microstructured surface. The two carriers are aligned and coupled such that, through the application of pressure and temperature either individually or together, composite rotatable-element components are formed.
In another embodiment of the present invention, composite rotatable-element components are assembled from rotatable-element components through the use of two carriers with microstructured surfaces so as to accommodate rotatable-element components of a a first class on a first carrier microstructured surface, and rotatable-element components of a second class on a second carrier microstructured surface. The rotatable-element components of each class are treated so as to preferentially bond to a rotatable-element component of a different class, and to bond only weakly, if at all, to a rotatable-element component of their own class. For example, the rotatable-element components can be treated electrically, magnetically, or chemically to accomplish such preferred bonding. The two carriers are aligned and coupled such that composite rotatable-element components are formed based on a minimization of the potential energy of interest associated with the bonding force.
In another embodiment of the present invention, composite rotatable-element components are assembled from rotatable-element components through the use of two carriers with microstructured surfaces so as to accommodate rotatable-element components of a first class on a first carrier microstructured surface, and rotatable-element components of a second class on a second carrier microstructured surface. The rotatable-element components of each class are treated so as to preferentially bond to a rotatable-element component of a different class, and to bond only weakly, if at all, to a rotatable-element component of their own class. For example, the rotatable-element components can be treated either electrically, magnetically, or chemically. The two classes are then dispersed into a mixing chamber and allowed to self-assemble such that composite rotatable-element components are formed based on a minimization of the potential energy of interest associated with the bonding force.
In another embodiment of the present invention, rotatable-element components of a first class and of a second class are created by any convenient means. The rotatable-element components of each class are treated so as to bond to a rotatable-element component of a different class, but to bond only weakly, if at all, to a rotatable-element component of their own class. For example, the rotatable-element components can be treated either electrically, magnetically, or chemically. The two classes are then dispersed into a mixing chamber and allowed to self-assemble such that composite rotatable-element components are formed based on a minimization of the potential energy of interest associated with the bonding force.
Still further, in another embodiment of the present invention, a laminate substrate containing a dense monolayer of composite rotatable-element components is created by the union of two carriers such that the combined microstructured surfaces form the containment structure within the laminate substrate. Furthermore, the rotatable-element components positioned within the microstructured carrier surfaces are bonded to form the desired composite rotatable-element components within the containment structure.
Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the process and apparatus particularly pointed out in the written description and claims herein as well as the appended drawings.